Add zstream redup command to convert deduplicated send streams

Deduplicated send and receive is deprecated.  To ease migration to the
new dedup-send-less world, the commit adds a `zstream redup` utility to
convert deduplicated send streams to normal streams, so that they can
continue to be received indefinitely.

The new `zstream` command also replaces the functionality of
`zstreamdump`, by way of the `zstream dump` subcommand.  The
`zstreamdump` command is replaced by a shell script which invokes
`zstream dump`.

The way that `zstream redup` works under the hood is that as we read the
send stream, we build up a hash table which maps from `<GUID, object,
offset> -> <file_offset>`.

Whenever we see a WRITE record, we add a new entry to the hash table,
which indicates where in the stream file to find the WRITE record for
this block. (The key is `drr_toguid, drr_object, drr_offset`.)

For entries other than WRITE_BYREF, we pass them through unchanged
(except for the running checksum, which is recalculated).

For WRITE_BYREF records, we change them to WRITE records.  We find the
referenced WRITE record by looking in the hash table (for the record
with key `drr_refguid, drr_refobject, drr_refoffset`), and then reading
the record header and payload from the specified offset in the stream
file.  This is why the stream can not be a pipe.  The found WRITE record
replaces the WRITE_BYREF record, with its `drr_toguid`, `drr_object`,
and `drr_offset` fields changed to be the same as the WRITE_BYREF's
(i.e. we are writing the same logical block, but with the data supplied
by the previous WRITE record).

This algorithm requires memory proportional to the number of WRITE
records (same as `zfs send -D`), but the size per WRITE record is
relatively low (40 bytes, vs. 72 for `zfs send -D`).  A 1TB send stream
with 8KB blocks (`recordsize=8k`) would use around 5GB of RAM to
"redup".

Reviewed-by: Jorgen Lundman <lundman@lundman.net>
Reviewed-by: Paul Dagnelie <pcd@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Matthew Ahrens <mahrens@delphix.com>
Closes openzfs#10124 
Closes openzfs#10156

cmd/Makefile.am

@@ -1,4 +1,4 @@
-SUBDIRS  = zfs zpool zdb zhack zinject zstreamdump ztest
+SUBDIRS  = zfs zpool zdb zhack zinject zstream zstreamdump ztest
 SUBDIRS += fsck_zfs vdev_id raidz_test zgenhostid
 
 if USING_PYTHON

cmd/zstream/.gitignore

@@ -0,0 +1 @@
+zstream

cmd/zstream/Makefile.am

@@ -0,0 +1,13 @@
+include $(top_srcdir)/config/Rules.am
+
+sbin_PROGRAMS = zstream
+
+zstream_SOURCES = \
+	zstream.c \
+	zstream.h \
+	zstream_dump.c \
+	zstream_redup.c
+
+zstream_LDADD = \
+	$(top_builddir)/lib/libnvpair/libnvpair.la \
+	$(top_builddir)/lib/libzfs/libzfs.la

cmd/zstream/zstream.c

@@ -0,0 +1,61 @@
+/*
+ * CDDL HEADER START
+ *
+ * This file and its contents are supplied under the terms of the
+ * Common Development and Distribution License ("CDDL"), version 1.0.
+ * You may only use this file in accordance with the terms of version
+ * 1.0 of the CDDL.
+ *
+ * A full copy of the text of the CDDL should have accompanied this
+ * source.  A copy of the CDDL is also available via the Internet at
+ * http://www.illumos.org/license/CDDL.
+ *
+ * CDDL HEADER END
+ */
+
+/*
+ * Copyright (c) 2020 by Delphix. All rights reserved.
+ */
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <ctype.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <strings.h>
+#include <unistd.h>
+#include <libintl.h>
+#include <stddef.h>
+#include <libzfs.h>
+#include "zstream.h"
+
+void
+zstream_usage(void)
+{
+	(void) fprintf(stderr,
+	    "usage: zstream command args ...\n"
+	    "Available commands are:\n"
+	    "\n"
+	    "\tzstream dump [-vCd] FILE\n"
+	    "\t... | zstream dump [-vCd]\n"
+	    "\n"
+	    "\tzstream redup [-v] FILE | ...\n");
+	exit(1);
+}
+
+int
+main(int argc, char *argv[])
+{
+	if (argc < 2)
+		zstream_usage();
+
+	char *subcommand = argv[1];
+
+	if (strcmp(subcommand, "dump") == 0) {
+		return (zstream_do_dump(argc - 1, argv + 1));
+	} else if (strcmp(subcommand, "redup") == 0) {
+		return (zstream_do_redup(argc - 1, argv + 1));
+	} else {
+		zstream_usage();
+	}
+}

cmd/zstream/zstream.h

@@ -0,0 +1,35 @@
+/*
+ * CDDL HEADER START
+ *
+ * This file and its contents are supplied under the terms of the
+ * Common Development and Distribution License ("CDDL"), version 1.0.
+ * You may only use this file in accordance with the terms of version
+ * 1.0 of the CDDL.
+ *
+ * A full copy of the text of the CDDL should have accompanied this
+ * source.  A copy of the CDDL is also available via the Internet at
+ * http://www.illumos.org/license/CDDL.
+ *
+ * CDDL HEADER END
+ */
+
+/*
+ * Copyright (c) 2020 by Delphix. All rights reserved.
+ */
+
+#ifndef	_ZSTREAM_H
+#define	_ZSTREAM_H
+
+#ifdef	__cplusplus
+extern "C" {
+#endif
+
+extern int zstream_do_redup(int, char *[]);
+extern int zstream_do_dump(int, char *[]);
+extern void zstream_usage(void);
+
+#ifdef	__cplusplus
+}
+#endif
+
+#endif	/* _ZSTREAM_H */

cmd/zstreamdump/zstreamdump.c → cmd/zstream/zstream_dump.c

@@ -42,6 +42,7 @@
 #include <sys/zfs_ioctl.h>
 #include <sys/zio.h>
 #include <zfs_fletcher.h>
+#include "zstream.h"
 
 /*
  * If dump mode is enabled, the number of bytes to print per line
@@ -58,17 +59,6 @@ FILE *send_stream = 0;
 boolean_t do_byteswap = B_FALSE;
 boolean_t do_cksum = B_TRUE;
 
-static void
-usage(void)
-{
-	(void) fprintf(stderr, "usage: zstreamdump [-v] [-C] [-d] < file\n");
-	(void) fprintf(stderr, "\t -v -- verbose\n");
-	(void) fprintf(stderr, "\t -C -- suppress checksum verification\n");
-	(void) fprintf(stderr, "\t -d -- dump contents of blocks modified, "
-	    "implies verbose\n");
-	exit(1);
-}
-
 static void *
 safe_malloc(size_t size)
 {
@@ -215,7 +205,7 @@ sprintf_bytes(char *str, uint8_t *buf, uint_t buf_len)
 }
 
 int
-main(int argc, char *argv[])
+zstream_do_dump(int argc, char *argv[])
 {
 	char *buf = safe_malloc(SPA_MAXBLOCKSIZE);
 	uint64_t drr_record_count[DRR_NUMTYPES] = { 0 };
@@ -273,26 +263,39 @@ main(int argc, char *argv[])
 		case ':':
 			(void) fprintf(stderr,
 			    "missing argument for '%c' option\n", optopt);
-			usage();
+			zstream_usage();
 			break;
 		case '?':
 			(void) fprintf(stderr, "invalid option '%c'\n",
 			    optopt);
-			usage();
+			zstream_usage();
 			break;
 		}
 	}
 
-	if (isatty(STDIN_FILENO)) {
-		(void) fprintf(stderr,
-		    "Error: Backup stream can not be read "
-		    "from a terminal.\n"
-		    "You must redirect standard input.\n");
-		exit(1);
+	if (argc > optind) {
+		const char *filename = argv[optind];
+		send_stream = fopen(filename, "r");
+		if (send_stream == NULL) {
+			(void) fprintf(stderr,
+			    "Error while opening file '%s': %s\n",
+			    filename, strerror(errno));
+			exit(1);
+		}
+	} else {
+		if (isatty(STDIN_FILENO)) {
+			(void) fprintf(stderr,
+			    "Error: The send stream is a binary format "
+			    "and can not be read from a\n"
+			    "terminal.  Standard input must be redirected, "
+			    "or a file must be\n"
+			    "specified as a command-line argument.\n");
+			exit(1);
+		}
+		send_stream = stdin;
 	}
 
 	fletcher_4_init();
-	send_stream = stdin;
 	while (read_hdr(drr, &zc)) {
 
 		/*